<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div>123</div>
  <button>按钮</button>

  <script>
    var btn = document.querySelector('button')
    var div = document.querySelector('div')

    btn.onclick = function() {
      div.style.backgroundColor = 'pink'
      div.style.width = '200px'
      div.style.height = '200px'
    }
  </script>
</body>
</html>